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Old 02-08-2012, 05:02 PM   #31
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Spray Foam vs. Fiberglass, anyone done the math?


My bad I thought we were talking about something other than an exterior polyiso rigid board insulating panels....oh wait. So your arguement is that foam MAY not last for eternity? What building materials will?? Should we reconsider using concrete? Wood rots eventually....

As far degrading in interior walls i've never heard of such a thing. I'd be willing to bet however that it was installation issue and ol' father time had little to do with it.

There have been great strides in the industry and it continues to become more enviromentally friendly and sustainable(soybased).

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Old 02-08-2012, 05:12 PM   #32
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Spray Foam vs. Fiberglass, anyone done the math?


A "small" problem I have read about w/ foam, that can not be cured (no pun intended), is spraying only between studs/rafters instead of a continuous layer. Wood shrinks a tad, and then you get a crack. So, were I to use spray foam, I'd ensure that there was a continuous layer over everything, just in case this cracking really does happen. I hope the spray foam industry continues to evolve, too.
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Old 02-08-2012, 05:13 PM   #33
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Spray Foam vs. Fiberglass, anyone done the math?


I am trying to figure out how to answer your post.

Foam will and has degraded r value over time. Does the foam itself? sometimes.....
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Old 02-08-2012, 05:22 PM   #34
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Spray Foam vs. Fiberglass, anyone done the math?


if you think soy based foam is great, spend a little time and read the MSDS.

Trust me, a lot of chemicals other than soy.....
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Old 02-08-2012, 05:35 PM   #35
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Spray Foam vs. Fiberglass, anyone done the math?


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Yes...Deplorable...current foams are made from oil. Being that oil IS finite and being consumed a mind boggling rate, it's safe to say an end WILL eventually come. The essence of sustainability is a product that is "natural" and therefore can be found readily available through the existence of earth (barring no apacolypse of course).

And thank you framer for the rea-world example. Foam degrades people...sorry to burst the "cure all" sentiment. Most rigid foam manufacturer's don't warranty their products for more than 20 years. And most pro-rate the R-value to accommodate the degredation over the lifetime. Polyiso, when blown, is around R-7+ an inch, but they advertise around R-6.5 an inch to account from degredation.
+1

Foams are worthwhile consideration but they are all oil based and you get nearly every bit of performance out of a properly designed and sealed wall assembly.
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Old 02-08-2012, 06:56 PM   #36
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Spray Foam vs. Fiberglass, anyone done the math?


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I am trying to figure out how to answer your post.
It doesn't seem to be worth the time, couple the handle with the logic and you're better off spending your time elsewhere...spraying stud/rafter bays is becoming increasingly shunned as the economic and secondary (refurbishing, remodeling) effects are become weighty enough to persuade most to alternative methods of insulation.

And to add to JK's comment about the wood shrinkage. This is real and closed cell foams are so rigid that they have troubles accomodating it. My uncle faced it himself a few months ago. It's similar to filling stud bays with grout and saying it won't crack...

Anywho...enjoy, I'll be unsubscribing from this post...
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Old 02-08-2012, 07:17 PM   #37
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Spray Foam vs. Fiberglass, anyone done the math?


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Here's one manufacturer noting the degredation of their polyiso foam: http://www.hpanels.com/images/storie...h/H-Shield.pdf

Notice on the Thermal values chart the asterisk next to "LTTR R VALUE" and the sentence below. The "weighted average" is the technical jargon to account for foam degredation over a 15 year period. Essentially if the foam is an R-7.5 when new and assuming constant degredation it would be approx. R-4.6 after 15 years making the average the R-6.0 as depicted.

AG you're comparing apples to oranges. You link to a rigid insulation product not spray foam. You wouldn't get the same seal with rigid sheets as with spray foam. Also, the "weighted average" takes other components of a wall into account such as framing and the effect of environmental temperature and wind on R-value. Obviously the R-value of a product with seams such as rigid insulation would fluctuate more over 15 years than a spray foam not necessarily proof of degradation.
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Old 02-08-2012, 09:34 PM   #38
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Spray Foam vs. Fiberglass, anyone done the math?


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AG you're comparing apples to oranges. You link to a rigid insulation product not spray foam. You wouldn't get the same seal with rigid sheets as with spray foam. Also, the "weighted average" takes other components of a wall into account such as framing and the effect of environmental temperature and wind on R-value. Obviously the R-value of a product with seams such as rigid insulation would fluctuate more over 15 years than a spray foam not necessarily proof of degradation.
Try not to confuse him more than he already is.
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Old 02-08-2012, 09:38 PM   #39
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+1

Foams are worthwhile consideration but they are all oil based and you get nearly every bit of performance out of a properly designed and sealed wall assembly.
I understand everyone's concern with foam being oil based. What the heck isn't though? I think there are much bigger fish to fry as far that arguement goes, and a well insulated, air sealed home like spray foam provides will save more over time than it uses.
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Old 02-08-2012, 09:40 PM   #40
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if you think soy based foam is great, spend a little time and read the MSDS.

Trust me, a lot of chemicals other than soy.....
I didn't say it was great, just a step in the right direction.
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Old 02-08-2012, 09:52 PM   #41
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A "small" problem I have read about w/ foam, that can not be cured (no pun intended), is spraying only between studs/rafters instead of a continuous layer. Wood shrinks a tad, and then you get a crack. So, were I to use spray foam, I'd ensure that there was a continuous layer over everything, just in case this cracking really does happen. I hope the spray foam industry continues to evolve, too.
That is possible. I haven't seen it personally. I had to remove drywall in my basement due to a window leak and I didn't see any signs cracking along the studs, though this was only 2 years after application. I would suspect any cracking would be pretty minimal. A much more common culprit of foam pulling from the studs is usually an applicator error by either spraying on too cold of substrate or spraying the foam at the wrong temp. Even a closed cell rigid foam has a some flex to it, unlike, say grout for example...
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Old 02-08-2012, 09:57 PM   #42
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Spray Foam vs. Fiberglass, anyone done the math?


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I understand everyone's concern with foam being oil based. What the heck isn't though? I think there are much bigger fish to fry as far that arguement goes, and a well insulated, air sealed home like spray foam provides will save more over time than it uses.
For one, cellulose is not oil based, but it ain't free of embodied energy, either; just better so. Foam, done well, will seal and insulate enough (for most locations), and it sure will therefor save energy. It is just that, IMO, it is not the best sole insulation in a wall. You can air seal down to Zipsville with plywood, airtight drywall approach, etc, so the argument that foam seals, though true enough, is not a great shout to use it just for that. Places that are nearly inaccessible or extremely tedious to work on properly? Spray foam 'em and be gone. Best luck to all; choosing "the best" ain't always straight forward.
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Old 02-09-2012, 09:44 PM   #43
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Spray Foam vs. Fiberglass, anyone done the math?


I used spray foam for a renovation a few years ago. We have a cottage with a membrane roof on the front that tends to get hot in summer. The rafters in that area were pretty shallow, not deep enough to put enough fiberglass in to keep things cool. So we shelled out for spray foam for that section of the ceiling, in order to stuff as much R into the rafters as possible. It does a nice job of keeping that area cool in the summer. I don't know what that saves energy-wise as I did it my first summer here, but it is comfortable. It was pricey, but I only did one 18' by 8' ceiling so it wasn't a big deal.

I wouldn't pay to do the whole house with it, but in tight spots or places with irregular cavities (irregular spaced joists in the floor, for example) it is not a bad way to go. The R value is nice but the real savings comes from ease of installation in these areas. Insulating a 70 year old crawlspace otherwise would be a real PITA.
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Old 02-22-2012, 05:41 PM   #44
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Spray Foam vs. Fiberglass, anyone done the math?


I used this site and they have a expanding foam insulation vs traditional insulation savings calculator...it might help. I like sprayfoam. If you follow the instructions it's really quite easy to do yourself. It's expensive but worth it in the long run. We redid our roof right before we inuslated and the amount of mold that was in the old blown cellulose was sick! One of the big selling features us, the expanding foam we chose to go with was that it is anitmicrobial.
Good luck!!

Last edited by FrancisABoyd; 02-22-2012 at 05:43 PM. Reason: I can't spell
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Old 02-22-2012, 07:33 PM   #45
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Spray Foam vs. Fiberglass, anyone done the math?


i've just been skimming through this topic. in the past year or so at we we've done a handful of home that have spray foam. i find it horrible stuff and i'd definitley use batt insulation on my own home. i work in the insurance industry and i have been hearing rumours that the next biggest thing in 10years or so is mold because the wood in new homes shrink so much that there are now gaps and cracks and after so many years ppl open walls to do renos. working with it suckksss, if the guys missed a spots shaving it down good luck putting drywall on and our nail pops have increased alot! and what about the spray foam the window and door guy uses, its not a spray foam thats rated as a vapour barrier. when you put in batt insulation you know its there and you know its good. the only positive thing i see with spray foam is the speed of it and it gets into hard to reach places. i'd batt my walls and hard to reach places like between my floor joists i'd spray to save time.

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